Among problems encountered by car drivers of late, the problem of bird droppings sticking to the coating film of the parked car, which droppings can be removed only with difficulty, and the problem of splashes of mud staining the car coating film as found after driving through wet weather, which necessitates washing of the car with rubbing, are of great concern. With the recent years' growth in demand for high-quality, maintenance-free cars, coating systems resistant to staining and capable of being deprived of stains in the event of staining have been demanded.
In car production lines, on the other hand, it is difficult to entirely prevent the occurrence of troubles due to adhesion of motes, dirt or the like. The coating film to which such a dirtying substance has adhered is repaired by recoating. In such cases, it has been common practice to remove the dirtying substance, polish the dirtied site, and recoat the polished site. From the work simplification and other points of view, coating systems capable of providing for a recoating film with good adhesion without polishing of the dirtied surface (hereinafter referred to as non-sanding recoatability) have been searched for.
Japanese Kokai Publication Hei-7-292313 describes an automotive coating composition capable of providing coating films well balanced among adhesion to the undercoat, scratch resistance, water resistance, oil resistance, weathering resistance, stain resistance and gloss which comprises a copolymer resulting from copolymerization of a silicone oligomer having ladder structure (hereinafter referred to as ladder silicone oligomer) having a specified molecular weight and a (meth)acryloxyalkyl group content in side chains of each molecule of 1 to 50% with at least one monomer selected from among (meth)acrylate esters, (meth)acrylamide, methylol(meth)acrylamide, alkoxymethylol(meth)acrylamides, unsaturated carboxylic acids, styrene and vinyl esters, as well as an organic solvent therefor, an ultraviolet absorber, an antioxidant and a crosslinking agent incorporated therein. In the automotive coating composition described in the above-cited publication Japanese Kokai Publication Hei-07-292313, the copolymer included ladder silicone oligomer (hereinafter referred to as ladder silicone copolymer), together with the crosslinking agent, constitutes the main component of the vehicle. From the non-sanding recoatability viewpoint, however, the composition is still unsatisfactory.